001    /*
002     * Licensed to the Apache Software Foundation (ASF) under one
003     * or more contributor license agreements.  See the NOTICE file
004     * distributed with this work for additional information
005     * regarding copyright ownership.  The ASF licenses this file
006     * to you under the Apache License, Version 2.0 (the
007     * "License"); you may not use this file except in compliance
008     * with the License.  You may obtain a copy of the License at
009     *
010     *     http://www.apache.org/licenses/LICENSE-2.0
011     *
012     * Unless required by applicable law or agreed to in writing, software
013     * distributed under the License is distributed on an "AS IS" BASIS,
014     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015     * See the License for the specific language governing permissions and
016     * limitations under the License.
017     */
018    package org.apache.hadoop.io.compress;
019    
020    import java.io.IOException;
021    import java.nio.ByteBuffer;
022    
023    import org.apache.hadoop.classification.InterfaceAudience;
024    import org.apache.hadoop.classification.InterfaceStability;
025    
026    /**
027     * Specification of a direct ByteBuffer 'de-compressor'. 
028     */
029    @InterfaceAudience.Public
030    @InterfaceStability.Evolving
031    public interface DirectDecompressor {
032      /*
033       * This exposes a direct interface for record decompression with direct byte
034       * buffers.
035       * 
036       * The decompress() function need not always consume the buffers provided,
037       * it will need to be called multiple times to decompress an entire buffer 
038       * and the object will hold the compression context internally.
039       * 
040       * Codecs such as {@link SnappyCodec} may or may not support partial
041       * decompression of buffers and will need enough space in the destination
042       * buffer to decompress an entire block.
043       * 
044       * The operation is modelled around dst.put(src);
045       * 
046       * The end result will move src.position() by the bytes-read and
047       * dst.position() by the bytes-written. It should not modify the src.limit()
048       * or dst.limit() to maintain consistency of operation between codecs.
049       * 
050       * @param src Source direct {@link ByteBuffer} for reading from. Requires src
051       * != null and src.remaining() > 0
052       * 
053       * @param dst Destination direct {@link ByteBuffer} for storing the results
054       * into. Requires dst != null and dst.remaining() to be > 0
055       * 
056       * @throws IOException if compression fails
057       */
058      public void decompress(ByteBuffer src, ByteBuffer dst) throws IOException;
059    }